Sound head



y 1942- J. c.' GRIFFiTH 2,282,960

SOUNDHEAD Filed May 19, 1939 Snventor dttorneg Patented May 12, 1942 "um'rac s'raras PATENT OFFICE 2,282,960 I SOUNDHEAD John C. Griffith,

Indianapolis, Ind, asslgnor to Radio Corporation of America-a, corporation of Deiaware Application May 19,1939, Serial No. 274,511

3 Claims.

particularly to an improvement 'in the rotary stabilizer type of soundhead such as is disclosed and claimed, for example, in Loomis et al., Patent No. 2,019,147. In the said Loomis patent there isdisclosed a soundhead wherein erg-photographic film sound record passes around a film drum with the sound track portion of the film overhanging the edge of the drum. Light from an appropriate exciter lamp is directed by an optical system through the sound track and is thereafter directed by prismatic lens to a. photo'- cell located at the opposite side of the drum. The film is drawn around the drum by a sprocket driven by an appropriate motor. The film drum (Ci. This invention relates to soundheads and more vided with a cast body i which forms a casing .and center plate and which-is provided with above referred to, the .various elements are 7 mounted directly on or in the center plate of the is carried on a shaft mounted on ball bearings.

This shaft carries at its other end a rotary stabilizer consisting of a magnesium alloy casing rigidly connected to the shaft and a flywheel freely rotatable within the casing and coupled thereto by an appropriate fluid medium, such as oil.

- The present invention improves on the construction of the Loomis et a1. soundhead in providing a resiliently mounted unit supporting the film drum and rotary stabilizer together with the exciter lens optical system and photocell. This unit is so mounted as to be free of soundhead vibrations produced either from the gearing or from the coupling of the soundhead with a 'picture projector and is constructed in an improved manner so as to secure a higher degree of precision in the relative mounting of the several parts than has been heretofore attainable, and to accomplish this at decreased manufacturing cost.

One object of the invention is to provide an improved soundhead.

Another object of the invention is to provide a soundhead which can be readily manufactured with a high degree of precision.

soundhead. Thepresent apparatus distinguishes therefrom in providing the aforesaid reproducer unit which is capable of separate fabrication and replacement. The reproducer unit includes a casting I! which, as shown, includes a slightly conical tubular member and a more or less fiat plate in a plane perpendicular to the axis of the tubular member and provided with a number.

of bosses. This casting i2 is first bored in the smaller end portions to provide the hollow cylindrical surfaces generally indicated at M and it.

This operation does not affect the intermediate portion i3 which is provided with sufficient clearance so that it needs no machining. The portions Id and it are bored to the same diameter and are thereafter reamed exactly to size by means of a pilot reamer so that both of these cylindrical surfaces will be accurate as to diam- Another object of the invention is to provide an improved method of making the mounting for the optical system and film drum of soundheads.

eter and they will be exactly in alignment with each other.

It is desired to the plate portion in a plane exactly the shaft 20. casting, after boring and reaming, is placed upon a mandrel and is rotated thereon in an appropriate machine such as a lathe and the surfaces of the bosses i5 and ii are turned flat while the casting is being thus rotated. This insures that both of these surfaces will be in a plane accurately perpendicular to the axis of rotation. During the same operation, the surfaces of the rear bosses a and 9, by which the reproducing provide the front surface of perpendicular to the axis of unit is secured tothe soundhead, are also turned as to be a force fiat and in a plane accurately perpendicular to I the axis of rotation.

After the foregoing operations are performed on the casting a sleeve 23, which is of such size fit in the bore i4, is pressed'into place by means This sleeve 23 is to just accommodate the ball bearing 2|, between of the casting with surfaces. I

In order to accomplish this, the

of a square shouldered arbor. pressed in to such a depth as the end of the sleeve and the face of the surface l1. After the ball bearing 2| is placed in position, it is secured by means of a circular washer 24 which is held in place by screws 25. The shaft 20 which is made integral with the film drum may then be inserted through the bearing 2|. A tubular sleeve 26, which serves as a spacer between the bearings, may then be placed over the shaft 2|) and the bearing 22 put into position. The bearing 22 is held in position by the collar 21, which fits snugly thereagainst and forces the bearing against the end of the sleeve 26. The rotary stabilizer 28 is placed on the shaft after the collar 21 and may be threaded on the shaft or may be secured by a nut on the shaft bearing against the outer face of the rotary stabilizer.

This clamps the rotary assembly comprising theshaft, the inner ball races and the sleeve 26 together and securely in position.

It will be apparent that the position of the film drum on the shaft is accurately determined in relation to the face IT by the positioning of the collar 23 which fixes the position of the bearing 2|. The reproducer unit may then have assembled therewith the optical system bracket 29, the prism mount 30 and the photocell socket and casing 3|, or these elements may be left off until after the reproducer unit is assembled with the soundhead. The reproducer unit is secured to the soundhead lugs by means of bolts 32 and 33 and a bolt passing the hole 34. Between the reproducer unit andeach lug there is provided an appropriate washer 36 of rubber or other resilient material. This washer has a tubular extension which passes through the hole in the lug II to prevent a direct contact between the bolt and the lug. A second rubber washer 35 is placed beneath the metal washer on the other end of the bolt. This arrangement thoroughly mechanically insulates the reproducing unit from the soundhead.

It will be apparent that these washers need not be of rubber, but may be of other appropriate material. For example, felt washers and a felt collar may be used, or one of the available synthetic materials may be used instead of rub ber, such, for example, as that known commer cially as Neoprene," which is a condensation product of Chloroprene.

I claim as my invention:

1. In a soundhead. a reproducing unit including a cast bracket resiliently supported in the soundhead, a rotatable assembly including a film drum, a shr and a rotary stabilizer mounted in said bracket, an exciter lamp and optical system mounted on said bracket on one side of the said film drum and a photocell mounted on said bracket on the other side'of said film drum.

2. The method of making a sound reproducer bracket comprising the steps of boring and reaming holes in accurate alignment in a tubul 'r member having a planar member at one e d thereof and in a plane substantially perpendicular to the axis of said tubular member, supporting said tubular member on a mandrel passing through said holes and facing off said planar member while rotating the bracket on said mandrel.

3. The method of making a sound reproducer bracket comprising the steps of boring and reaming holes in accurate alignment in a tubular member having a planar member at one end thereof and in a plane substantially perpendicular to the axis of said tubular member, supporting said tubular member on a mandrel passing through said holes and facing off said planar. member while rotating the bracket on said mandrel, and thereafter pressing a sleeve into one of said holes to deflnethe position of a bearing.

JOHN c. GRIFFITH.- 

